Liquid detergent compositions, usually in solution or emulsion form, have been employed as all-purpose detergents and have been suggested for cleaning hard surfaces such as painted woodwork, bathtubs, sinks, tile floors, tiled walls, linoleum, paneling and washable wallpaper. Many such preparations, such as those described in U.S. Pat. Nos. 2,560,839, 3,234,138, and 3,350,319 and British Patent Specification No. 1223739, include substantial proportions of inorganic phosphate builder salts, the presence of which can sometimes be found objectionable for environmental reasons and also because they necessitate thorough rinsing of the liquid detergent from the cleaned surface to avoid the presence of noticeable depositings of phosphate thereon. In U.S. Pat. Nos. 4,017,409 and 4,244,840 liquid detergents of reduced phosphate builder salt contents have been described but such may still require rinsing or can include enough phosphate to be environmentally objectionable. Some liquid detergents have been made which are phosphate-free, such as those described in U.S. Pat. No. 3,935,130, but these normally include higher percentages of synthetic organic detergent which increased detergent content may be objectionable due to excessive foaming during use that can result from its presence. The previously described liquid detergent compositions are emulsions but are not disclosed to be microemulsions like those of the present invention.
Microemulsions have been disclosed in various patents and patent applications for liquid detergent compositions which may be useful as hard surface cleaners or all-purpose cleaners, and such compositions have sometimes included detergent, solvent, water and a co-surfactant. Among such disclosures are European Patent Specification Nos. 0137615, 0137616, and 0160762, and U.S. Pat. No. 4,561,448, all of which describe employing at least 5% by weight of the solvent in the compositions. The use of magnesium salts to improve grease removing performance of solvents in microemulsion liquid detergent compositions is mentioned in British Patent Specification No. 2144763. Other patents on liquid detergent cleaning compositions in microemulsion form are U.S. Pat. Nos. 3,723,330, 4,472,291, and 4,540,448. Additional formulas of liquid detergent compositions in emulsion form which include hydrocarbons, such as terpenes, are disclosed in British Patent Specifications Nos. 1603047 and 2033421, European Specification No. 0080749, and U.S. Pat. Nos. 4,017,409, 4,414,128, and 4,540,505. However, the presence of builder salt in such compositions, especially in the presence of magnesium compounds, tends to destabilize the microemulsions and therefore such builders are considered to be undesirable.
Although the cited prior art relates to liquid all-purpose detergent compositions in emulsion form and although various components of the present compositions are mentioned in the art, it is considered that the art does not anticipate or make obvious subject matter disclosed and claimed herein. In accordance with the present invention a stable aqueous microemulsion cleaning composition, which may be in concentrated or dilute form, comprises at least two different anionic synthetic organic detergent, a water insoluble organic compound, water and a co-surfactant system, which co-surfactant system adjusts interfacial conformation to reduce interfacial tension at interfaces between dispersed and continuous phases of an emulsion to produce a stable concentrated microemulsion which is stable at temperatures in the range of 5.degree. to 50.degree. C. and which has a pH in the range of 1 to 11. Such concentrated microemulsions are dilutable with water to at least five times their weight, to produce diluted liquid detergent compositions which are often also stable aqueous microemulsions which are useful as all-purpose cleaning compositions. Both the concentrated and diluted compositions are effective for cleaning oily and greasy soils from substrates, and when the compositions are acidic they are also useful to remove lime scale and soap scum from hard surfaces, such as bathroom fixtures, floors and walls.
Furthermore, the present inventors have observed that in formulations containing grease-removal assisting magnesium compounds, the addition of minor amounts of builder salts, such as alkali metal polyphosphates, alkali metal carbonates, nitrilotriacetic acid salts, and so on, tends to make it more difficult to form stable microemulsion systems.
In addition to microemulsion concentrates, the present invention also relates to dilute microemulsions to processes for manufacturing such microemulsions and to processes for cleaning surfaces with them.